This invention is directed to the achievement of a terminal device having an improved retention portion for retaining the device in a hole in a panel-like member such as a printed circuit board. The herein disclosed embodiment of the invention comprises a terminal post however, the principles of the invention can be used with other terminal devices.
Terminal posts having rectangular cross-sections are widely used in the electrical industry in conjunction with printed circuit boards and panel boards for making electrical connections between, and among, electrical circuits. For example terminal posts on a panel board are frequently used for point to point wiring requirements by connecting predetermined posts to each other with wires which are connected to the individual posts by wrap-type or clip-type terminations. It is also common practice to use multi-contact electrical connectors with terminal posts, the connectors having socket-type contact terminals therein which are mated with the posts on the panel or printed circuit board.
One method of mounting the terminal posts on the board is to provide the posts with an enlarged portion which is dimensioned to have a force fit in the hole of a printed circuit board or panel. The post is simply driven into the board or staked to the board and the resulting interference fit is relied upon to hold the post on the board. The staking method gives rise to several troublesome problems and its shortcomings have long been recognized. For example, the panel or PC board may be severely damaged as a result of driving the oversized portion of the post into the hole. The board may be chipped and, if the hole is plated with conducting material, the plating may be badly scored or even broached from the hole. If the staking method is used on printed circuit boards, the portion of the printed circuitry on a surface of the board may be lifted therefrom while the staking operation is being carried out and the damage thus caused may render the board completely useless. Even if there is no significant damage to the panel or board, the effect of staking a large number of terminal posts may give rise to internal stresses in the board which in turn, cause it to assume a curved or arcuate shape rather than a flat plane. Finally, the force required to drive a post into an undersized hole is quite high and the insertion machinery must be undesirably robust to carry out the operation.
The problems encountered with the staking process described above have inspired the proposal of alternative methods of mounting terminal posts or other terminal devices in circular holes. For example, it has been proposed that a portion of the terminal post be formed as a spring member capable of deflecting during insertion and exerting a frictional force against the walls of the hole after insertion.
The instant invention is specifically directed to the achievement of an improved retention means which can be imparted to terminal posts during manufacture thereof by a few relatively simple stamping and forming methods.
It is among the objectives of the invention to provide a retaining means on a terminal device such as a terminal post or the like having characteristics which permit the terminal device to be inserted into a hole without unduly high insertion forces being required. A further object is to provide a spring-type retaining means on a terminal device which can be used in post-receiving holes which may vary between relatively wide limits as regards hole diameter. A further object of the invention is to provide a retaining means on a terminal post or the like which will not cause damage to the panel or printed circuit board into which it is inserted or to the circuitry thereon and will not give life to distortion in the panel or printed circuit board which might arise from unduly high internal stresses.